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Effect of cognition

III. Effect of water intake on cognition

Cognitive implications of water supplementation and immediate effects of water intake were mostly studied in children because they are known to be at particular risk of water deficit, and because it is ethically difficult to restrict water intake in children (Masento et al. 2014). In children, water intakes of 200 to 650mL have been shown to immediately reduce thirst and to increase subjective happiness, memory, motor skills, visual attention and visual search (Benton and Burgess 2009; Booth et al. 2012; Edmonds and Burford 2009; Edmonds and Jeffes 2009). Over the course of one class day, Fadda et al. asked children to increase their fluid intake with 1.0L of water (mean increase was actually of 625mL over the day). As compared to children who did not drink additional water, children who drank reported higher vigor and performed better at short-term memory tasks (Fadda et al. 2012). More recently, in their cohort study led on 447 undergraduates, Pawson et al. found that students who brought water to the exam performed better although they did not actually measure the water volumes consumed (Pawson et al. 2013).

 

In adults, water ingestion following a period of fluid restriction and/or fasting was repeatedly found to enhance state of arousal, increasing cognitive dimensions such as alertness, attention and reaction time, and decreasing perception of confusion (Edmonds et al. 2013b; Neave et al. 2001; Pross et al. 2013). When water intake occurs without previous fluid deprivation, water still appears to enhance alertness and visual attention (Edmonds et al. 2013a; Rogers et al. 2001). However, several studies found that the beneficial effect of water intake on state of arousal depends on whether or not subjects were thirsty before they drank water (Edmonds et al. 2013b; Rogers et al. 2001).

 

Headaches have been reported in subjects under induced dehydration (Armstrong et al. 2012). On recurrent migraine patients, Spigt et al. found that an increase in water intake of at least 0.8L per day can reduce headaches and increase patients’ quality of life (Spigt et al. 2005; Spigt et al. 2012).

 

Immediate effects of water intake were repeatedly found on state of arousal, improving perceptions of vigor, as well as performance on task requiring attention and alertness. In children, water also appears to enhance short-term memory.

Figure 4. Commonly reported benefits of water intake on mood state and cognitive function.

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